Re: No RX or TX after changing frequency


 

I assume that the start was the click - click problem that is usually a short in the control head taking out the 8 volt from the main board. 
After that was resolved I again assume that you had the 8 volt from the main to the panel and then the +5 and the +3.3 volt supplies alive and well.
It is possible that at that point you have another problem in the head. When the control head gets power the cpu sends a signal that it is alive and ready to the main cpu where the relay is not dropped out.
I suspect that a second problem was created when working in the head.
I believe the PWK signal makes a ground that pulls down the device that initiates the POWER ON SEQUENCE.
I would trace that signal to find out why the relay is no longer pulling in. PWK goes to the  IC1302 to initiate turning on.
The control head has no voltage on it until the relay pulls in.
The voltage present should be the voltage pulled down by the power switch. Check for that voltage on the switch at the transfer jack pin 2.
After the relay pulls in 8 volts at pin 1. 
I hope memory serves and it helps you fix your radio.
J.D.
KE4MD


On Mon, Dec 28, 2020 at 8:12 PM Peter via groups.io <pp-1-3-5-7-9=yahoo.com.tw@groups.io> wrote:
Hi Barron,

Thank you for your information , in actually , I have been replaces all these four (28 pin x2 and 30 pin x2 ) FFC ribbon cables with new one , but the problem still happen .  from the beginning when I press the power button the rig just response with click and click and can not power on ,  since my rig been suffered with the front panel with a short capacitor and caused a 4.7 ohm resister for 8V regulator get burnout in the main board , So, I had double check it and the capacitor and the 4.7 ohm resister all are ok , Therefore,  I have clean the contact pins between the main body and the front panel also replace all the four ribbon cables , but finally, the problem with no Rx after I either changing the frequency by turn the VFO or Microphone . 

Anyway , Thank you again ,  and I will keeping to dig the the root caused .



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J.D. Barron

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